Tire noise and vibration are of great significance to tire designers and manufacturers. Subjective judgments of the road worthiness of a tire are usually based on the driver's "feel" of the tire response. Tire noise often reaches the driver's ears as a component of the interior noise of the car while tire vibration is transmitted through various mechanical linkages such as the steering column. To minimize such noise and vibration, it is necessary to understand the role the dynamics of the tire have in transmitting the forces generated by uneven road surfaces and tire anomalies to the suspension system of the vehicle, particularly at high speeds. Since the mechanical properties of the tire are altered considerably by the type of load and suspension system supported, the dynamics of the tire cannot be determined in isolation, but measurements of the dynamic response of the tire must be made while the tire is supporting a representative dynamic load.
It is most desirable that a system be provided for assessing the dynamic response of a tire to various road surfaces under realistic loading conditions. To achieve this condition, a suspension simulator, replicating such a realistic dynamic load, would necessarily simulate the dynamics of a load bearing suspension system of a selected vehicle within a laboratory setting. Accordingly, the selection of tires for a new vehicle could be conducted in a laboratory to identify those tires best suited to produce the smoothest and quietest conditions for occupants of the vehicle.
It is further desired that an analytical method be developed to study the dynamic response of the tire subjected to a systematic variation of road surfaces and dynamic loading conditions. Data obtained from the implementation of a suspension simulator can be used for such a purpose. Using such data, determinations can be made as to the extent that tire dynamics are influenced by the dynamics of a vehicle suspension system. In addition to providing support data for the tire selection process as mentioned above, such a study may also provide viable information to those attempting to model the dynamic response of a tire through the finite element method or other similar methods.
In general, it is most desirable that a suspension simulator be provided to allow tire designers to investigate modal coupling between an automobile suspension and the associated tire. Such modal coupling is the dynamic interaction between these two systems each of which can resonate at various frequencies. By configuring the suspension simulator such that its dynamic characteristics may be varied to replicate the dynamic characteristics of a given automobile suspension system, a designer may develop a tire for the given automobile without having to bring the automobile to the test facility itself. Indeed, the dynamic characteristics of the vehicle suspension system may be obtained from the vehicle manufacturer.
It has been determined that the assessment of the dynamics of a rolling tire within a laboratory environment requires the determination of a number of criteria. The magnitude and phase of the unsteady forces transmitted from the road surface of the rolling drum, endless belt, or similar device to the tire must be measured. The magnitude and phase of the unsteady forces and velocity transmitted to the wheel axle must be measured. The magnitude and phase of the reaction forces generated by the dynamic load on the wheel axle must be representative of an actual or conceptual suspension system. Finally, gradual changes in the components of the dynamic load must be implemented during rolling conditions to assess the effect of such changes on tire dynamics, for small changes in the resonance of a suspension system can cause large changes in the tire dynamics.